I disabled all of my gallery plugins and unfortunately the problem remains. Upon activation of NextGEN I receive the same error message.
Thank you for your help with this, my provider does meet all those requirements. I am unfortunately unable to follow the other steps because this message appears as soon as I log in, my dashboard is completely unavailable. To access my dashboard I would first need to disable NextGEN through FTP which would render me unable to activate it again without this error message returning.
I can confirm that I have two other gallery plugins active on my WordPress – is this likely to create a conflict?